My third COVID-19 vaccine dose

I have just got my third COVID-19 vaccine dose, 9 months after my second one and 11 months after the first one.

I would call myself a vaccine-hesitant person. This means that I have always considered the pros and cons of any vaccination, just as I do for any medical treatment. I was vaccinated against COVID-19 in February and April 2021.

When the campaign to give the third dose was announced, I decided to wait. I tested my antibody levels in September 2020 and they were reasonably high (1119.0(U/mL)).

Although I was perfectly aware of all the caveats associated with the relationship between the antibodies levels and coronavirus protection, I thought I was reasonably safe with additional protection measures like masks and working from home so that I might not need additional booster protection.

The infection numbers were dropping in Scotland at that time and restrictions and mask-wearing was continuing. It was clear that at some point a new variant would come and so I decided to wait until the vaccines are updated and to get a booster sometime later in 2022.

However, the rise of the new highly infectious variant, Omicron, has changed the picture for me. I have had to re-evaluate the balance between risks associated with the treatment itself and risks and benefits associated with the disease.

How do I calculate these risks, and how does Omicron change this picture?

The COVID-19 associated risk is composed of two factors: becoming infected and getting seriously ill if I get it.

I believe that the risk of becoming infected with Omicron is now much higher than it was for Delta back in Summer and Autumn 2021. This is because Omicron is more infectious. Also, people generally are no longer willing to avoid contact or to wear masks.

I am aware of a risk associated with COVID-19 disease. Even if Omicron appears to be milder, I believe that my own risk of complications from COVID-19 is significantly higher than the risks associated with vaccination (I am immuno-compromised due to an ongoing medical treatment). This might not be true for others and I respect the fact that people might weigh these factors differently.

Infection fatality ratio (for the pre-Omicron period) compared with the estimate for vaccine death rate based on “yellow notes” reporting (July 2021); Marc Brevand and AK

I am aware of all the risks associated with vaccination. As a scientist with an interest in medicine, I have read the medical literature and I understand the statistics underlying the reports. I myself have analysed the “yellow card” reports of reported side effects.

According to the graphs above, my own chances of dying if I get COVID-19 are between 0.2% and 2% (a disclaimer: I am 60 years old), possibly higher. According to my analysis, the probability of dying following the vaccination is 0.003%. This is not 0% – I know there are risks associated with “taking the jab”, but about 200 times lower than for the disease itself.

I did the above analysis in July 2021. With Omicron, even though the risk of getting serious complications if infected is lower, on the balance I now believe my overall risk of becoming infected, landing in critical care and dying, has not gone down enough to be below the risk of complications following the “booster” vaccination.

In my analysis above I have particularly looked at hospitalisation or death following either infection or vaccination, although I am also aware of all other side effects. I am also aware that there might be long-term side effects to the vaccination which we do not know about, just as there might be long term consequences of catching COVID-19 (“long-Covid”). These factors nevertheless do not change my view of the relative risks.

All the above arguments are concentrating on my own risk. But, by vaccinating I am also helping others. The evidence for a decrease in the transmission is not very strong, but by protecting myself from complications – if I get infected – I am protecting the NHS from becoming overwhelmed. How?

The first two vaccines already provide massive protection levels, but the booster further reduces my chances of landing in critical care:

(20) Paul Mainwood on Twitter: “ICNARC have updated their analysis of COVID patients in critical care in England, Wales and NI. They now show boosted patients as well. They are shown in green. Yes, I’ve put them on the chart. You have to squint.” / Twitter

If I got infected and if I required hospitalisation, I would be taking space and resources from somebody who perhaps needs them more now – a patient with cancer, a patient with heart disease, or one requiring dialysis.

I hope the above analysis will help those who are thinking of either being vaccinated the first time, or the second time, or the third time. I fully respect that having read the above you will come to a different conclusion.


In May 2022 I finally caught COVID-19. I wrote about this experience on this blog. The symptoms were similar to a moderately severe flu lasting for a couple of days. Other members of the family, with different prior vaccination statuses, fared similarly.

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